1. Field of the Invention
The invention relates to form feed apparatus of the type wherein pin feed tractor mechanisms are employed to feed relatively wide edge perforated pin hole paper into, through and out of the printer, stacker or other similar device. More particularly, the invention relates to form feed apparatus wherein the tractors are adjustably movable transverse to the line of paper movement.
2. Description of the Prior Art
In printing, feeding and stacking devices of the type employing multilayered sheet material which is provided with lateral perforations in which conveyor belts carrying pin elements engage the holes in the paper to move the paper, it is necessary to be able to laterally adjust such feeding devices to accommodate varying widths of paper; from relatively narrow paper to relatively wide paper. And, because the tractor driving mechanism must be accurately positionable, the tractors must be capable of being locked in position once the desired width has been set. This preset condition should be reasonably fixed so that the paper does not yaw in its travel across the tractor in which case the perforations may tear or the drive may become erratic. In the past a number of different devices have been utilized to secure the tractor mechanism to the transverse moving means each one of which is deficient in one or more particulars. For example, one type utilizes a nut and bolt which has a two part clamp such that adjustment of the nut on the bolt tightens or loosens the clamp. Obviously a problem arises should the operator back off the nut too far in which case the two pieces may fall away from the tractor mechanism. This is not only inefficient and time consuming to adjust but tends to make for non-accurate operation of the tractor due to the need for physical manipulation of parts. Other mechanisms of a similar type have releases coupled with the tractor overlay guide so that when the overlay guide is tilted back to expose the pins of the tractor mechanism for the paper, the clamp releases and the tractor may be moved from side to side. These devices are relatively complex and because of the number of moving parts including springs and cams, tend to get out of adjustment relatively easily; tend to wear and require rather large amounts of maintenance.
The present tractor locking mechanism is relatively simple, does not require any space outside the form feed so that the feed fitted with the device can be moved close up against a housing wall or against the neighboring form feed. The locking element is simple enough that no maintenance is required and the pressure on the transverse support mechanism is relatively easily adjustable for any desired transducer load and any varying types width forms.